(Received 24 September 2012;accepted 9 October 2012;online 20 October 2012)

The title mol­ecule, C17H14F3NO4, consists of two nearly planar fragments, viz. the 2-benzyl­oxypyridine (r.m.s. deviation 0.016 Å) and (E)-3-meth­oxy­prop2-enoic (r.m.s. deviation 0.004 Å) units, which form a dihedral angle of 84.19 (7)°. In the crystal, pairs of O—H⋯O hydrogen bonds link mol­ecules into dimers that are further connected by C—H⋯O and C—H⋯F inter­actions into (001) layers. In addition, π–π stacking inter­actions are observed within a layer between the pyridine and benzene rings [centroid–centroid distance = 3.768 (2) Å]. The F atoms of the trifluoro­methyl group are disordered over two sets of sites in a 0.53 (4):0.47 (4) ratio.

The above compound is the acid metabolite of picoxystrobin, which is a systemic fungicide of strobilurin group with broad spectrum bio-efficacy against various diseases of economically important agricultural crops (Balba, 2007; Ammermann et al., 2000).

In (I) (Fig.1), all bond lengths and angles are normal and correspond to those observed in the related structure (Kant et al., 2012). The dihedral angle between the two aromatic rings is 1.93 (9)°. The propenoic acid fragment is nearly perpendicular to the attached benzene ring [dihedral angle 82.6 (1)°]. The two nearly planar fragments, 2-(benzyloxy)-3-(trifluoromethyl)pyridine unit (r.m.s. deviation 0.016Å) and (E)-3-methoxyprop2-enoic unit (r.m.s. deviation 0.004Å) form dihedral angle of 84.19 (7)°. The F atoms of the trifluoromethyl group were refined as disordered over two sets of sites with occupancies of 0.53 (4)/0.47 (4). In the crystal, O—H···O hydrogen bonds link molecules to form dimers (Table 1). Dimers are further connected by C—H···O and C—H···F hydrogen bonds into (001) layers (Fig. 2). The crystal structure is further stabilized by π–π interactions between the pyridine ring (C11—C15/N1) of the molecule at (x, y, z) and the benzene ring of an inversion related molecule at(1 - x, 1 - y, - z) [centroid separation = 3.768 (2) Å, interplanar spacing = 3.437 Å and centroid shift = 1.54 Å].

The title compound is the acid metabolite of picoxystrobin [systematic name: methyl (E)-3-methoxy-2-{2-[6-(trifluoromethyl)-2-pyridyloxymethyl]phenyl}acrylate], a systemic fungicide of the strobilurin group with broad-spectrum bio-efficacy against various diseases of economically important agricultural crops, see: Balba (2007); Ammermann et al. (2000). For a related structure, see: Kant et al. (2012).

Picoxystrobin (0.353 g, 0.001 mol) was dissolved in 5 ml of acetone and to it 5 ml of 1 N NaOH solution was added. The reaction mixture was refluxed at 343 K for 6 h, and then cooled. The compound was precipitated by neutralizing with 1 N HCl solution. The precipitated compound was dissolved in methanol and crystallized by the process of slow evaporation.(m.p. 415 K).

H atom bonded to O atom was located in a difference map and refined freely. Other H atoms were positioned geometrically and were treated as riding on their parent C atoms, with C—H distances of 0.93–0.97 Å and with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(methyl C). In the refinement process restraints were imposed on C-F distances of the disordered molecular fragments.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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